Final answer:
The disappearance of Abigail and Mercy is preceded by a collection of mysterious and urgent events involving characters suddenly leaving or being taken from places of work or revelry, often under strange or unexplained circumstances.
Step-by-step explanation:
The events that precede the sudden disappearance of Abigail and Mercy involve a series of mysterious and clandestine activities. These events begin with individuals, including a white-haired man and his family, entering a mountain through what seems to be a trap-door. There are also instances of unexpected commands and quick movements as executioners are hustled into an elevator, and scenes of silent and deserted revelries leading to speculation about supernatural occurrences. Further, there are moments when key characters like Jane Withersteen and Lassiter witness the departure of loved ones, and scenes of employees leaving their work unexpectedly.
Through these examples, we witness a progression of sudden departures and abandonments, each driven by different motives and surrounded by various emotions, from fear and urgency to resolution and peaceful resignation. These can be considered as significant plot events leading up to the disappearance of Abigail and Mercy from the narrative.